The performance improvement of electronic devices such as bipolar transistors and field-effect transistors has dramatically increased the operating speed of large-scale integrated circuits (LSI). However, although achieving performance improvement, the scaling down of transistors has caused a serious problem with electrical interconnects therebetween in relation to the increase of the electrical line resistance and the capacitance between adjacent electrical line, which is becoming a bottleneck in the improvement of LSI performance.
In view of the foregoing problem with electrical interconnects, some proposals have been made for an optically interconnected LSI, where the elements therein are optically interconnected. The optical interconnect has marginal frequency dependence of loss at frequencies from DC to 100 GHz or more. Furthermore, the interconnect path suffers from no electromagnetic interference. Hence interconnection at several 10 Gbps or more can be easily realized.
For the purpose of integration into an LSI, the semiconductor light emitting device serving as a light source for optical interconnects needs to be easily coupled to a light waveguide for transmitting light and to be highly adaptable to LSI processes. For use as a light source for intra-LSI optical interconnection, a silicon-based light emitting device is desirable. For example, a silicon-based semiconductor light emitting device is disclosed in Japanese Journal of Applied Physics, Vol. 45, No. 27 (2006) p. L679 (hereinafter referred to as Non-Patent Document 1).
The device disclosed in Non-Patent Document 1 is a light emitting diode that emits light by spontaneous emission. Because its operating speed is restricted by carrier lifetime, there is little hope for fast operation.